Broad and direct interaction between TLR and Siglec families of pattern recognition receptors and its regulation by Neu1

Chen, Guo Yun; Brown, Nicholas K.; Wu, Wei; Khedri, Zahra; Yu, Hai; Chen, Xi; Vlekkert, Diantha van de; d’Azzo, Alessandra; Zheng, Pan; Liu, Yang

doi:10.7554/elife.04066

Cited by 122 publications

(146 citation statements)

References 52 publications

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“…In a recent study, it was shown that many Siglecs (including Siglec-E) can bind to sialic acids on Toll-like receptors and could potentially act as a brake to slow down or resolve inflammation (13). Removal of sialic acids with sialidase Neu1 can disrupt this interaction, resulting in activation of inflammatory processes.…”

Section: Cd33-related Siglecs Are a Family Of Proteins Widely Expressmentioning

confidence: 99%

Studies on the Detection, Expression, Glycosylation, Dimerization, and Ligand Binding Properties of Mouse Siglec-E

Siddiqui

Schwarz

Springer

et al. 2017

Journal of Biological Chemistry

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Edited by Amanda F. Fosang CD33-related Siglecs are a family of proteins widely expressed on innate immune cells. Binding of sialylated glycans or other ligands triggers signals that inhibit or activate inflammation.Immunomodulation by Siglecs has been extensively studied, but relationships between structure and functions are poorly explored. Here we present new data relating to the structure and function of Siglec-E, the major CD33-related Siglec expressed on mouse neutrophils, monocytes, macrophages, and dendritic cells. We generated nine new rat monoclonal antibodies specific to mouse Siglec-E, with no cross-reactivity to Siglec-F. Although all antibodies detected Siglec-E on transfected human HEK-293T cells, only two reacted with mouse bone marrow neutrophils by flow cytometry and on spleen sections by immunohistochemistry. Moreover, whereas all antibodies recognized Siglec-E-Fc on immunoblots, binding was dependent on intact disulfide bonds and N-glycans, and only two antibodies recognized native Siglec-E within spleen lysates. Thus, we further investigated the impact of Siglec-E homodimerization. Homology-based structural modeling predicted a cysteine residue (Cys-298) in position to form a disulfide bridge between two Siglec-E polypeptides. Mutagenesis of Cys-298 confirmed its role in dimerization. In keeping with the high level of 9-O-acetylation found in mice, sialoglycan array studies indicate that this modification has complex effects on recognition by Siglec-E, in relationship to the underlying structures. However, we found no differences in phosphorylation or SHP-1 recruitment between dimeric and monomeric Siglec-E expressed on HEK293A cells. Phylogenomic analyses predicted that only some human and mouse Siglecs form disulfide-linked dimers. Notably, Siglec-9, the functionally equivalent human paralog of Siglec-E, occurs as a monomer. Two broad groups of Siglecs are identified based on their patterns of evolution. Sialoadhesin, CD22, myelin-associated glycoprotein (MAG) and Siglec-15 are highly conserved and show few changes among species (2). In contrast, CD33-related Siglecs evolve rapidly in mammals (2, 9). As there are not clear functional orthologs between primates and rodent Siglecs, these receptors are assigned an alphabetic letter in rodents and a number in primates. Siglec-E, the main CD33-related Siglec in mouse, was first discovered by a yeast two-hybrid screen using SHP-1 as a bait (10). Studies using a sheep polyclonal Siglec-E antibody specific for the ectodomain indicated that Siglec-E is expressed on neutrophils, macrophages, monocytes, dendritic cells, and a subset of Natural killer cells (11). The organ with the * This work was supported, in whole or in part, by National Institutes of Health Grants P01HL107150 and R01GM32373 (to A. V.). The authors declare that they have no conflicts of interest with the contents of this article. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. □ S Th...

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Section: Cd33-related Siglecs Are a Family Of Proteins Widely Expressmentioning

confidence: 99%

Studies on the Detection, Expression, Glycosylation, Dimerization, and Ligand Binding Properties of Mouse Siglec-E

Siddiqui

Schwarz

Springer

et al. 2017

Journal of Biological Chemistry

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“…Therefore, here the levels of TNF-␣ protein are used as readout of endotoxin tolerance. TNF-␣ in the culture supernatants was measure using the CBA Beads kit as previously described (23)(24)(25). As shown in Fig.…”

Section: Sialylation Of Cell Surface Was Significantly Increased On Lmentioning

confidence: 99%

“…Previously, we found that Siglec G/10-CD24 interaction selectively represses the NF-B-driven inflammatory response to danger-associated molecular patterns (DAMPs), 2 but not pathogen-associated molecular patterns (PAMPs) (23,24). Recently, we reported extensive and direct interactions between Siglecs and Toll-like receptors (TLRs) and dendritic cells from Siglece-deficient mice demonstrated increased responses to all TLR ligands tested (25). However, whether Siglecs contribute to the development of endotoxin tolerance is still unknown, and further experimental investigation is needed to delineate this and identify effective targets for sepsis therapy.…”

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confidence: 99%

Induction of Siglec-1 by Endotoxin Tolerance Suppresses the Innate Immune Response by Promoting TGF-β1 Production

Lan

Ren

et al. 2016

Journal of Biological Chemistry

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Sepsis is one of the leading causes of death worldwide. Although the prevailing theory for the sepsis syndrome is a condition of uncontrolled inflammation in response to infection, sepsis is increasingly being recognized as an immunosuppressive state known as endotoxin tolerance. We found sialylation of cell surface was significantly increased on LPS-induced tolerant cells; knockdown of Neu1 in macrophage cell line RAW 264.7 cells resulted in enhanced LPS-induced tolerance, whereas overexpression of Neu1 or treatment with sialidase abrogated LPS-induced tolerance, as defined by measuring TNF-␣ levels in the culture supernatants. We also found that the expression of Siglec-1 (a member of sialic acid-binding Ig (I)-like lectin family members, the predominant sialic acid-binding proteins on cell surface) was specifically up-regulated in endotoxin tolerant cells and the induction of Siglec-1 suppresses the innate immune response by promoting TGF-␤1 production. The enhanced TGF-␤1 production by Siglec-1 was significantly attenuated by spleen tyrosine kinase (Syk) inhibitor. Knockdown of siglec-1 in RAW 264.7 cells resulted in inhibiting the production of TGF-␤1 by ubiquitin-dependent degradation of Syk. Mechanistically, Siglec-1 associates with adaptor protein DNAX-activation protein of 12 kDa (DAP12) and transduces a signal to Syk to control the production of TGF-␤1 in endotoxin tolerance. Thus, Siglec-1 plays an important role in the development of endotoxin tolerance and targeted manipulation of this process could lead to a new therapeutic opportunity for patients with sepsis.Sepsis is generally defined as a systemic inflammatory response syndrome in response to infection. Sepsis can be potentially life threatening; of more than 1 million Americans who are diagnosed with severe sepsis every year, between 28 and 50% will die from this disease (1, 2). It is well-recognized that patients with sepsis are often immune suppressed, a state of reduced responsiveness to endotoxin known as endotoxin tolerance, deaths in this immunosuppressive phase are typically due to failure to control the secondary infections (3-5). The molecular mechanisms underlying this endotoxin tolerance phenomenon is poorly understood.Sialic acids are a family of nine-carbon acidic monosaccharides and are involved in immune response, such as host-pathogen recognition, migration, and antigen presentation. Mounting experimental evidence suggests that the presence of sialic acid residue act as a marker of self in the immune system, as such residues are absent from most microbes (6). Indeed, host cells can be lysed by immune cytotoxic effector mechanisms after extensive desialylation, an observation that demonstrates the significant role played by cell surface sialic acids in the selfrecognition process (7). In addition, normal human serum contains natural antibodies to sialidase-treated red blood cells (7-9), lymphocytes (10), and thymocytes (7). Recently, Meesmann et al. showed that desialylation acted as an "eat me" signal and caused an enhanced upt...

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“…Of these, Neu3 is predomi nantly localized in the plasma membrane, and both Neu1 and Neu4 have been found to translocate to the cell surface under certain conditions, while Neu2 is a cytosolic enzyme [104]. Neu5Ac2en 14, and its C5 glycolamido analog, have been shown to disrupt that activity of Neu1 at the cell surface [123]. Studies using recombinant human sialidases, showed that 4-deoxy-4-guanidino-Neu5A c2en 5 produces only weak inhibition of Neu1 (IC 50 2.7 mM) and Neu4 (IC 50 0.5 mM), but a micromolar level of inhibition against Neu2 (IC 50 16 μM) and Neu3 (IC 50 6.8 μM) [124].…”

Section: Selectivity For Influenza Virus Sialidase Over Human Sialidasesmentioning

confidence: 99%

Development of Influenza Virus Sialidase Inhibitors

Pascolutti

Thomson

Itzstein

2016

Methods and Principles in Medicinal Chemistry

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Broad and direct interaction between TLR and Siglec families of pattern recognition receptors and its regulation by Neu1

Cited by 122 publications

References 52 publications

Studies on the Detection, Expression, Glycosylation, Dimerization, and Ligand Binding Properties of Mouse Siglec-E

Studies on the Detection, Expression, Glycosylation, Dimerization, and Ligand Binding Properties of Mouse Siglec-E

Induction of Siglec-1 by Endotoxin Tolerance Suppresses the Innate Immune Response by Promoting TGF-β1 Production

Development of Influenza Virus Sialidase Inhibitors

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